"Contemplating is receiving." (St. John of the Cross) What we receive in prayer is the Spirit, who makes all creation new, moment by moment. It is the Spirit who rebirths us within the caves of our hearts. The case is a metaphor for this silent withdrawal, this going away to be alone, to listen, to gestate the Spirit, to rebirth ourselves. The reborn self is the child of wisdom born in solitude.
Sabbath time is a time when we turn our attention to what is holy, to what is sacred, to what is important. It's a time when we allow the clamor of the world to fall away and we listen for the still, small voice of God. It's a time when we allow ourselves to be embraced by the love of God, to rest in that love, and to be renewed and refreshed by it.